minsyms.c

早期freebsd实现

  msym_bunch -> contents[msym_bunch_index].name = (char *) name;
  msym_bunch -> contents[msym_bunch_index].address = address;
  msym_bunch -> contents[msym_bunch_index].info = NULL;
  msym_bunch -> contents[msym_bunch_index].type = ms_type;
  msym_bunch_index++;
  msym_count++;
}

void
prim_record_minimal_symbol_and_info (name, address, ms_type, info)
     const char *name;
     CORE_ADDR address;
     enum minimal_symbol_type ms_type;
     char *info;
{
  register struct msym_bunch *new;

  if (msym_bunch_index == BUNCH_SIZE)
    {
      new = (struct msym_bunch *) xmalloc (sizeof (struct msym_bunch));
      msym_bunch_index = 0;
      new -> next = msym_bunch;
      msym_bunch = new;
    }
  msym_bunch -> contents[msym_bunch_index].name = (char *) name;
  msym_bunch -> contents[msym_bunch_index].address = address;
  msym_bunch -> contents[msym_bunch_index].info = NULL;
  msym_bunch -> contents[msym_bunch_index].type = ms_type;
    /* FIXME:  This info, if it remains, needs its own field.  */
  msym_bunch -> contents[msym_bunch_index].info = info;  /* FIXME! */
  msym_bunch_index++;
  msym_count++;
}

/* Compare two minimal symbols by address and return a signed result based
   on unsigned comparisons, so that we sort into unsigned numeric order.  */

static int
compare_minimal_symbols (fn1p, fn2p)
     const PTR fn1p;
     const PTR fn2p;
{
  register const struct minimal_symbol *fn1;
  register const struct minimal_symbol *fn2;

  fn1 = (const struct minimal_symbol *) fn1p;
  fn2 = (const struct minimal_symbol *) fn2p;

  if (fn1 -> address < fn2 -> address)
    {
      return (-1);
    }
  else if (fn1 -> address > fn2 -> address)
    {
      return (1);
    }
  else
    {
      return (0);
    }
}

/* Discard the currently collected minimal symbols, if any.  If we wish
   to save them for later use, we must have already copied them somewhere
   else before calling this function.

   FIXME:  We could allocate the minimal symbol bunches on their own
   obstack and then simply blow the obstack away when we are done with
   it.  Is it worth the extra trouble though? */

/* ARGSUSED */
void
discard_minimal_symbols (foo)
     int foo;
{
  register struct msym_bunch *next;

  while (msym_bunch != NULL)
    {
      next = msym_bunch -> next;
      free ((PTR)msym_bunch);
      msym_bunch = next;
    }
}

/* Compact duplicate entries out of a minimal symbol table by walking
   through the table and compacting out entries with duplicate addresses
   and matching names.  Return the number of entries remaining.

   On entry, the table resides between msymbol[0] and msymbol[mcount].
   On exit, it resides between msymbol[0] and msymbol[result_count].

   When files contain multiple sources of symbol information, it is
   possible for the minimal symbol table to contain many duplicate entries.
   As an example, SVR4 systems use ELF formatted object files, which
   usually contain at least two different types of symbol tables (a
   standard ELF one and a smaller dynamic linking table), as well as
   DWARF debugging information for files compiled with -g.

   Without compacting, the minimal symbol table for gdb itself contains
   over a 1000 duplicates, about a third of the total table size.  Aside
   from the potential trap of not noticing that two successive entries
   identify the same location, this duplication impacts the time required
   to linearly scan the table, which is done in a number of places.  So we
   just do one linear scan here and toss out the duplicates.

   Note that we are not concerned here about recovering the space that
   is potentially freed up, because the strings themselves are allocated
   on the symbol_obstack, and will get automatically freed when the symbol
   table is freed.  The caller can free up the unused minimal symbols at
   the end of the compacted region if their allocation strategy allows it.

   Also note we only go up to the next to last entry within the loop
   and then copy the last entry explicitly after the loop terminates.

   Since the different sources of information for each symbol may
   have different levels of "completeness", we may have duplicates
   that have one entry with type "mst_unknown" and the other with a
   known type.  So if the one we are leaving alone has type mst_unknown,
   overwrite its type with the type from the one we are compacting out.  */

static int
compact_minimal_symbols (msymbol, mcount)
     struct minimal_symbol *msymbol;
     int mcount;
{
  struct minimal_symbol *copyfrom;
  struct minimal_symbol *copyto;

  if (mcount > 0)
    {
      copyfrom = copyto = msymbol;
      while (copyfrom < msymbol + mcount - 1)
	{
	  if (copyfrom -> address == (copyfrom + 1) -> address
	      && (strcmp (copyfrom -> name, (copyfrom + 1) -> name) == 0))
	    {
	      if ((copyfrom + 1) -> type == mst_unknown)
		{
		  (copyfrom + 1) -> type = copyfrom -> type;
		}
	      copyfrom++;
	    }
	  else
	    {
	      *copyto++ = *copyfrom++;
	    }
	}
      *copyto++ = *copyfrom++;
      mcount = copyto - msymbol;
    }
  return (mcount);
}

/* Add the minimal symbols in the existing bunches to the objfile's
   official minimal symbol table.  99% of the time, this adds the
   bunches to NO existing symbols.  Once in a while for shared
   libraries, we add symbols (e.g. common symbols) to an existing
   objfile.  */

void
install_minimal_symbols (objfile)
     struct objfile *objfile;
{
  register int bindex;
  register int mcount;
  register struct msym_bunch *bunch;
  register struct minimal_symbol *msymbols;
  int alloc_count;

  if (msym_count > 0)
    {
      /* Allocate enough space in the obstack, into which we will gather the
	 bunches of new and existing minimal symbols, sort them, and then
	 compact out the duplicate entries.  Once we have a final table,
	 we will give back the excess space.  */

      alloc_count = msym_count + objfile->minimal_symbol_count + 1;
      obstack_blank (&objfile->symbol_obstack,
		     alloc_count * sizeof (struct minimal_symbol));
      msymbols = (struct minimal_symbol *)
		 obstack_base (&objfile->symbol_obstack);

      /* Copy in the existing minimal symbols, if there are any.  */

      if (objfile->minimal_symbol_count)
        memcpy ((char *)msymbols, (char *)objfile->msymbols, 
		objfile->minimal_symbol_count * sizeof (struct minimal_symbol));

      /* Walk through the list of minimal symbol bunches, adding each symbol
	 to the new contiguous array of symbols.  Note that we start with the
	 current, possibly partially filled bunch (thus we use the current
	 msym_bunch_index for the first bunch we copy over), and thereafter
	 each bunch is full. */
      
      mcount = objfile->minimal_symbol_count;
      
      for (bunch = msym_bunch; bunch != NULL; bunch = bunch -> next)
	{
	  for (bindex = 0; bindex < msym_bunch_index; bindex++, mcount++)
	    {
	      msymbols[mcount] = bunch -> contents[bindex];
#ifdef NAMES_HAVE_UNDERSCORE
	      if (msymbols[mcount].name[0] == '_')
		{
		  msymbols[mcount].name++;
		}
#endif
#ifdef SOME_NAMES_HAVE_DOT
	      if (msymbols[mcount].name[0] == '.')
		{
		  msymbols[mcount].name++;
		}
#endif
	    }
	  msym_bunch_index = BUNCH_SIZE;
	}

      /* Sort the minimal symbols by address.  */
      
      qsort (msymbols, mcount, sizeof (struct minimal_symbol),
	     compare_minimal_symbols);
      
      /* Compact out any duplicates, and free up whatever space we are
	 no longer using.  */
      
      mcount = compact_minimal_symbols (msymbols, mcount);

      obstack_blank (&objfile->symbol_obstack,
	(mcount + 1 - alloc_count) * sizeof (struct minimal_symbol));
      msymbols = (struct minimal_symbol *)
	obstack_finish (&objfile->symbol_obstack);

      /* We also terminate the minimal symbol table
	 with a "null symbol", which is *not* included in the size of
	 the table.  This makes it easier to find the end of the table
	 when we are handed a pointer to some symbol in the middle of it.
         Zero out the fields in the "null symbol" allocated at the end
	 of the array.  Note that the symbol count does *not* include
	 this null symbol, which is why it is indexed by mcount and not
	 mcount-1. */

      msymbols[mcount].name = NULL;
      msymbols[mcount].address = 0;
      msymbols[mcount].info = NULL;
      msymbols[mcount].type = mst_unknown;

      /* Attach the minimal symbol table to the specified objfile.
	 The strings themselves are also located in the symbol_obstack
	 of this objfile.  */

      objfile -> minimal_symbol_count = mcount;
      objfile -> msymbols = msymbols;
    }
}